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B. BROIDO Oct. 29, 1929.

SAFETY VALVE FOR HIGH PRESSURE BOILERS Filed May 29, 1926 jrar'oa 1N VEN TOR.

A TT ORNE Y.

PATENT QFFIGE BENJAMIN BROIDO, I-IEVJ YORK, N. Y., ASSIGNOR TO THE SUIPERHEATER COMPANY, OF NEW YORK, Y.

SAFETY VALVE FEB HIG RESSURE BOILERS a I to release excess pressu e on so-called pressures of 600 to 1500 s. or more nor 5 l 1 In true even if, as is too natural tendency, th

drums are made of as small diameters as admissible. his great wall thickness makes such drums expensive. both on account of the material used and of the dii'iiculty of manufacture. In fact there are only few establishments that have facilities to manufacture such drums at all as riveting them is out of the question and forging; out of a solid billet must be resorted to. This small size of the steam and water drums involves a small cubical content of the steam space and results in rather wide pressure fluctuations with relatively slight variations in the load. In other words if the load drops oil by even a small amount the pressure in the boiler rises much more quicl y than it the steam space were larger,

and on the other hand if the load momentarily increases even by slight amount the withdrawal of the additional amount of steam from the boiler results in a rapid and disproportionately large pressure drop. The result of these conditions is that the safety valve is called into action more frequently than is the ease with boilers of more moderate pressures.

il ion the safety valve is called into action with such a high pressure boiler the wear and tear on the valve is very severe. The seat and disc of the valve are much more rapidly eroded and the spring deteriorate much more rapidly when the valve operates between a pressure of 1200 or 1500 lbs. and atmospheric pressure than is the case where a safety valve releases pressure from 200 lbs. to atmospheric pressure. Moreover, it is a matter of common observation that such a valve delivering steam from a pressure of 1200 or 1500 lbs. to atmospheric pressure does not work as smoothly as one working; within narrov limits.

It is the purpose of the present invention to obviate these dilliculties.

The invention is illustrated in the single figure of the drawing herewith which shows a portion of the steam drum of a high pres sure boiler with my invention applied.

The steam drum of the high pressure boiler is slrown at 1. The safety valve through which steam leaves the boiler in the first place shown at 2. This safety valve is not in itself novel, but may be of any preferred form. In the form illustrated the valve proper 3 is ield on its seat by the spring 4. Steam enters the valve 5 and when the valve is opened by an excess pressure in the boiler leaves the valve through the opening 6.

instead of allowing the steam to escape to atmosphere from the opening 6 I propose to lead it to a chamber 7 to which is attached a second. safety valve 8, which may be similar in constr etion to the safety valve 2. This second safety valve is adjusted to operate when the pressure in chamber 7 rises to a point intermediate the boiler pressure and atmospheric. From this valve 8 the steam nay he allowed to escape directly to atmosphere in some cases or, as in the case illus trated in the drawing, it is carried to an additional chamber 9 from which a third safety valve 10 relieves surplus steam to the atmosphere through opening 11. This third valve is adjusted to open when the pressure in chamber 9 is at some point intermediate the pressure prevailing in 7 and atmospheric pressure. These pressures in the boiler and in the two chambers 7 and 9 may for example be follows: 1200 lbs. per square inch in the boiler, 600 lbs. in the chamber 7 and 300 in the chamber 9. The valve 2 will open when the boil r pressure exceeds 1200 lbs. valve 8 will open when the pressure in 7 rises above 600 and valve 10 will open when the pressure in 9 exceeds 300. These pressures, it will be understood, are used only for illustrative purposes. In some cases it will be suliicient to use only two safety valves and in some cases it may prove advisable to use more than three. In any case the valves will be set to operate at successively diminishing pressures. The valves will increase successively in size proportionately to the increased volume of the steam as it escapes through them.

The operation of this arrangement involves the fact that the flow of steam from a space or chamber of higher pressure to one of lower pressure is not materially all'ected by raising the pressure of the lower pressure chamber, provided this pressure is not raised beyond fifty-eight percent of that prevailing in the chamber 01 higher pressure. To apply this to the present case, the rate of flow from the boiler at 1200 lbs. through the safety valve 2 is not materially lowered by allowing it to eX- haust into the space 7 where the pressure is 600 lbs. over what it would be if it exhausted directly into atmosphere. Similarly the flow from 7 through the safety valve 8 is not materially lowered by the arrangement shown and described from what it would be if this valve opened directly to atmosphere. The wear and tear on each of the valves, however, is very materially diminished and the valves each work much more smoothly than it they ope ated between the wider limits.

The advantage otthe arrangement will at once be apparent. By it the frequency with which the safety valve has to be ground or repaired is lessened and in addition the operation of the boiler becomes safer and steadier. These advantages are more than sullicient to offset the cost of the extra valves and pressure chambers.

It will be obvious that the form of my invention which I illustrate and describe herein may be varied in some respects without sacrificing the inventive idea.

What I claim is:

1. In apparatus of the class described, the combination of a boiler drum; a series or" steam chambers; a corresponding series of safety valves connecting the drum to the first chamber, the chambers in series to each other and the last chamber to the atmosphere, the several safety valves bein so adjusted that the pressure in each of the steam spaces is about one half as high as in the preceding one.

2. A con'ibination according to claim 1, the safety valves being so adjusted that the pressure in no steam space exceeds 58 per cent of that in the preceding space.

The method of releasing excess steam from a high-pressure boiler by permitting it to expand from boiler pressure to atmospheric pressure in a succession of stages each of which leaves the steam at a pressure substan tially half that of the preceding stage.

4. The method of releasing excess steam from a high-pressure boiler in accordance with claim 3, the steam pressure at no stage exceeding 58 per cent oi that of the preceding stage.

BENJAMIN BROIDO.

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